This invention relates to medical surgical instruments for delivery of an anaesthetic drug. The invention is more particularly concerned with instruments for use in the delivery of an anaesthetic for use as a nerve block.
The use of a needle to locate a nerve using electrical impulses delivered to the nerve through the tip of the needle has been known for many years. See, for example, Sarnoff, S. J. and Sarnoff, L. C.; Prolonged Peripheral Nerve Block by Means of Indwelling Plastic Catheter Treatment of Hiccup; 1950. The location of the nerve is followed by insertion of anaesthetic through the needle so that it emerges from the tip of the needle and contacts the nerve.
An alternative procedure is disclosed in U.S. Pat. No. 6,190,370 to Tsui. This procedure involves the proper positioning of the stimulating needle and the introduction of a stimulating catheter through the needle. Once properly placed adjacent the nerve and into the plexus sheath of the patient, again utilizing electrical stimulation delivered through the catheter to determine placement, the stimulating catheter may then be used to deliver variable amounts of anaesthetic for use as a nerve block.
U.S. Pat. No. 6,456,874, to Hafer et al., which has at least one inventor in common with the present disclosure, discloses an electrical wire clipped or otherwise electrically attached to the needle is also well known in the art. The wire may, alternatively, be rigidly attached to the proximal end of the needle with the plastic hub of the needle holding the wire in place. Electrical stimulation is provided to the wire and, through the wire, to the needle for the purpose of locating the nerve. U.S. Pat. No. 6,456,874 also discloses the above described needle and catheter combination as well as an integral conductive wire contained in the catheter, through which an electrical current may be applied to determine correct positioning of the catheter once it has been inserted through the needle. An electrical impulse sent through the conductive wire is utilized in determining proper placement of the tip of the catheter and, thus, the point at which the anaesthetic will be delivered.
Also disclosed in the U.S. Pat. No. 6,456,874 is utilizing the needle and catheter in combination. The electrified needle is first used to locate a nerve generally. Once generally located, electrical stimulation is ceased through the needle and the catheter is inserted through the needle and into the nerve. electrical stimulation of the catheter is also commenced. Manipulation of the electrified catheter and the physiological results of this manipulation are closely monitored to optimize placement of the distal tip of the catheter. Once properly placed, anaesthetic may be delivered to the desired nerve location.